Generally, a lash adjuster is configured to include a body and a plunger. The body is fixed to a mounting concavity of a cylinder head. The plunger can move up and down in this body. The plunger has an upper end portion protruding from the body, and this upper end portion of the plunger supports a rocker arm. A low-pressure chamber is provided in the plunger, while a high-pressure chamber is formed in the lower space of the body. The lower space is bounded by a bottom wall of the plunger. A valve port is opened in a bottom wall of the plunger, and a valve body is provided in the high-pressure chamber. The valve body is biased in a direction to close the valve port. The valve body can open and close the valve port.
Operation of the lash adjuster is as follows. As the plunger moves up at a time of starting the engine, the valve port accordingly opens so that oil in the low-pressure chamber is drawn into the high-pressure chamber. At this time, if the level of operating oil in the low-pressure chamber is low, the air in the low-pressure chamber can be drawn into the high-pressure chamber and can cause abnormal noise. As a countermeasure of this, there is an art that stores a large amount of operating oil in the low-pressure chamber in advance and thereby prevents drawing of the air into the high-pressure chamber. For example, Patent Document 1 as below discloses a lash adjuster that has an oil supply passage as a means for store the large amount of operating oil in the low-pressure chamber. In this art, operating oil is supplied through this oil supply passage substantially up to the oil level of the top end of the plunger so that the operating oil level in the low-pressure chamber is at the higher level.    [Patent Document 1] Japanese Unexamined Patent Application Publication 2005-2953